London , England -LRB- CNN -RRB- -- China will execute within a few hours a British man convicted of smuggling heroin , his family said Monday .

Akmal Shaikh , 53 , has been informed by the Chinese authorities that he will be executed , said Seema Khan and Latif Shaikh , first cousins of the condemned man .

The relatives told CNN that Shaikh 's mother had not been informed of his execution , scheduled for Tuesday morning . `` We are keeping the news away from her , '' Khan said . `` We do n't feel she can take the news and bear the brunt of it . ''

Shaikh has exhausted all his legal appeals .

The Chinese government is not known to give 11th-hour reprieves . But Khan and Shaikh said they are nevertheless `` hoping the Chinese government will show some compassion . ''

Shaikh 's supporters maintain he is mentally ill and that Chinese officials did not take that into account when trying him .

A United Nations official has asked China not to go forward with the execution . Philip Alston , the U.N. special rapporteur on extrajudicial executions , has said it would be a `` major step backwards for China '' to execute a mentally ill man .

`` Both Chinese and international law clearly indicate that a person who committed a crime while suffering from significant mental illness should not be subjected to the death penalty , '' Alston said in a statement released by Reprieve , a British legal group .

`` I very much hope that the government will grant clemency in this case . ''

Britain too has asked China not to execute Shaikh .

`` The British Government has been doing and will continue to do everything within its power to secure a fair trial and clemency on the death penalty for Akmal Shaikh , '' a Downing Street spokesman said Monday .

`` The prime minister has intervened personally on a number of occasions : he has raised the case with Premier Wen -LRB- Jiabao -RRB- , most recently at the Copenhagen summit ; and has written several times to President Hu -LRB- Jintao -RRB- . At every level ... the government has raised its concerns , made clear our opposition to the death penalty , and requested a full mental health assessment . We will remain engaged in the coming hours . ''

China says it has followed the law .

`` This case has always been handled according to law . During the trial , the defendant has been guaranteed his legal rights , '' Jiang Yu , spokeswoman for China 's Ministry of Foreign Affairs , said last week . `` Everyone knows that international drug smuggling is a grave crime . ''

Shaikh was convicted of carrying up to 4 kilograms -LRB- almost 9 pounds -RRB- of heroin at the Urumqi Airport in September 2007 . His final appeal -- to the People 's Supreme Court -- was rejected a week ago .

He would be the first European Union citizen executed in China in 50 years , Reprieve said .

The organization says Shaikh may be suffering from bipolar disorder , which is characterized by delusional and manic behavior . The group says Chinese authorities have refused requests for Shaikh to be examined by a doctor and for his mental condition to be taken into account during his trial and sentencing .

`` We deeply regret that mental health concerns had no bearing on the final judgment despite requests by Mr. Shaikh 's defense lawyer and repeated calls by the prime minister , ministers , members of the opposition , as well as -LSB- the -RSB- European Union , '' the British Foreign Office said last week .

A spokesman for China 's Ministry of Foreign Affairs told CNN in October there was no evidence of mental illness .

`` The British Embassy and a British organization proposed to have a psychological exam but could not offer any proof of mental illness , '' the spokesman said . `` The defendant himself said that his family does not have a history of mental illness . ''

Shaikh said he was given a suitcase to carry by another man who had duped him into believing he was traveling to China to become a nightclub performer , and was unaware that the bag contained drugs .

Reprieve campaigners have revealed details of Shaikh 's erratic lifestyle prior to his arrest -- including traveling to Poland to start an airline and then on to Central Asia to become a pop star .

While living in Poland , Shaikh was approached by a man who helped him write a song that Shaikh believed would bring world peace , according to Reprieve .

The man said he knew people in Kyrgyzstan who could help Shaikh become a pop star . Once there , Shaikh was introduced to another man called Okole , who told him he owned a nightclub in China where they would launch his singing career .

The pair traveled together to Tajikistan , staying in a five-star hotel .

Okole then told Shaikh he would have to travel on to China himself because there was only one seat available on the plane -- and gave him the suitcase to carry , according to Reprieve .

Forensic psychologist Peter Schaapveld said he suspects Shaikh is suffering from a severe mental disorder .

Schaapveld traveled to Urumqi this year for Shaikh 's appeal hearing but was unable to meet Shaikh or attend the appeal . He said British consular staff told him court officials had been `` bemused and amused '' by Shaikh 's `` incoherent '' testimony .

Schaapveld also examined hundreds of pages of rambling e-mails sent by Shaikh to the British Embassy in Poland and various public figures , including then-U.S. President George W. Bush and former Beatle Paul McCartney .

He said the evidence `` very clearly '' suggested Shaikh was `` probably suffering from bipolar disorder and may also have an additional delusional psychosis . ''

CNN 's Jo Ling Kent in Beijing and Zain Verjee and Simon Hooper in London contributed to this report .

@highlight

China will execute British man convicted of smuggling heroin within hours , his family says

@highlight

Akmal Shaikh supporters maintain he is mentally ill and officials did not take that into account when trying him

@highlight

British government has asked China not to execute Shaikh but China says it has followed law